A lead is a special wire that delivers energy from a device, such as a pacemaker or implantable cardioverter defibrillator (ICD), to the heart muscle. One major type of lead tip has a small helix screw at the end (see FIG. 1B) in order to remain attached to the heart muscle, and is referred to as an active-fixation lead. Another major type of lead tip is referred to as a passive-fixation lead which has soft “tines” at rise tip of the lead (see FIG. 1A). The small plastic tines become passively “stuck” to the muscle in the heart and subsequent growth of scar tissue. The body's natural healing process typically forms scar tissue along the lead and at its tip within a few months of implantation, which fastens it even more securely in the patient's body. Leads usually last longer than the batteries that power the device to which they are attached.
Occasionally, however, these leads have to be removed, or extracted, even though they are designed to be implanted permanently in the body. Device infection is the most common reason for lead extraction. It is usually impossible to cure the infection without completely removing all hardware from the body if any part of the system becomes infected. This requires removal of the device from the chest wall, as well as removal of all leads from the veins and heart.
Sometimes a lead fails to work properly (e.g., due to a break in the metal wire or surrounding insulation) and is another reason requiring lead extraction. A less common reason for lead extraction is a mechanical lead failure, such as a protruding wire, that could be dangerous to the patient.
Leads run a fairly long course from the device, through the veins, and into the heart (see FIG. 2). Scar tissue may form at multiple sites along the lead due to the body's natural healing process. This scar tissue can create strong attachments of the lead to the wall of a blood vessel or a wall of a heart chamber. Freeing a lead from these attachments requires considerable skill and experience and is considered to be more difficult and risky than implanting the lead in the first place. Leads can be extracted from an access point located in the shoulder area or the leg area. Specialized tools are used to remove pacemaker and ICD leads from the inside of the heart. The most common approach follows the course of the lead through the subclavian vein under the patient's shoulder.
Current technologies for lead extraction utilize power sheaths, which deliver various forms of energy to the tip of the sheath, as well as mechanical cutter and dilation sheaths. As the sheath is pushed over the lead and advances to an area of scar tissue attachment, the operator can activate the sheath's cutting source functionality (energy, mechanical, dilation) to cut, dilate, heat, or vaporize the scar tissue. This has the effect of freeing the lead from its attachment points, allowing the lead to be removed with much less force. The lead can be pulled out of the body safely once the entire lead is freed from scar tissue attachments. One type of power sheath uses electro-cautery, similar to what is used to cut through tissue in surgery. Another type of power sheath has a ring of fiber optics that delivers laser energy at its tip (see FIG. 3). The lasers, when activated, vaporize water molecules in the scar tissue approximately within one mm of the tip. This allows the sheath to be passed slowly over the entire lead all the way to the heart, after which, the lead can be removed through the lumen of the sheath.
However, during some procedures, the tip of the power sheath is not adequate to provide the stabilization necessary for effective tip removal, which may cause an excessive amount of damage to the heat wall. Each time the lead is separated from scar tissue, there is a small chance of tearing the surrounding blood vessel or perforating the heart, which can result in major bleeding in the chest or around the heart. Thus, there is a need in the art for a better way to stabilize the area around the lead tip so that damage to the heart is minimized when removing the lead tip.